Syntheses, characterization and ethylene polymerization of half-sandwich group IV metal complexes with tridentate [O,N,S] ligands

Abstract

A series of half-sandwich group IV metal complexes with tridentate monoanionic phenoxy-imine arylsulfide [O−NS] ligand [2-But4-Me-6-((2-(SC6H5)C6H4N=CHC6H2O)]− (La) and dianionic phenoxy-amine arylsulfide [O−N−S] ligand [2-But4-Me-6-((2-(SC6H5)C6H4N-CH2C6H2O)]2− (Lb) have been synthesized and characterized. Lb was obtained easily in high yield by reduction of ligand La with excess LiAlH4 in cool diethyl ether. Half-sandwich Group IV metal complexes CpTi[O−NS]Cl2 (1a), CpZr[O−NS]Cl2 (1b), CpTi[O−N−S]Cl (2a), CpZr[O−N−S]Cl (2b) and Cp*Zr[O−N−S]Cl (2c) were synthesized by the reactions of La and Lb with CpTiCl3, CpZrCl3 and Cp*ZrCl3, and characterized by IR, 1H-NMR, 13C-NMR and elemental analysis. In addition, an X-ray structure analysis was performed on ligand Lb. The title Group IV half-sandwich bearing tridentate [O,N,S] ligands show good catalytic activities for ethylene polymerization in the presence of methylaluminoxane (MAO) as co-catalyst up to 1.58 × 107 g-PE·mol-Zr−1·−1. The good catalytic activities can be maintained even at high temperatures such as 100 °C exhibiting the excellent thermal stability for these half-sandwich metal pre-catalysts.